Shaft drive device

ABSTRACT

With the disclosure shaft drive device, has a PCB device ( 1, 1 ′); a rotor device ( 50; 5, 51 ) with a rotor ( 5 ) and a rotor shaft ( 51 ) attached to it; and a stator device ( 40 ) for driving the rotor ( 5 ) with the rotor shaft ( 51 ); an attachment device ( 60 ) for attaching the rotor device ( 50; 5, 51 ) and the stator device ( 40 ) to the PCB device ( 1, 1 ′) in such a way that the PCB device ( 5 ) forms part of the frame, surrounding the rotor shaft, of the shaft drive device.

BACKGROUND OF THE INVENTION

The present invention relates to a shaft drive device, having: a PCB(printed circuit board) device; a rotor device with a rotor and a rotorshaft attached to it; and a stator device for driving the rotor with therotor shaft.

Although in principle it can be used for arbitrary shaft drive devices,the present invention and the problems it seeks to solve will beexplained in terms of a shaft drive device for use in a gauge/controlinstrument or combination instrument of a motor vehicle, for instance asa pointer shaft drive device for the pointer of a gauge instrument.

In a modern gauge/control instrument or combination instrument of amotor vehicle, many functions are now provided. Although a number ofdigital gauge instruments are used, nevertheless for the sake ofexpediency, some pointer instruments are also used, which each require apointer shaft drive device.

It is quite conventional to mount such a shaft drive device, forinstance a stepping motor, as an independent component on a PCB deviceand put it in contact with the PCB device. However, this kind ofprocedure is complicated and expensive from a production standpoint andrequires a large amount of space for installation.

The problems the present invention seeks to solve accordingly reside increating an economical, space-saving and easily installed shaft drivedevice, in particular for use in a gauge/control instrument orcombination instrument of a motor vehicle.

SUMMARY OF THE INVENTION

Accordingly, it is an object of present invention to provide a shaftdrive device which avoids the disadvantages of the prior art.

In keeping with these objects and with these objects and with otherswhich will become apparent hereinafter, one feature of present inventionresides, briefly stated, in a shaft drive device, which has a printedcircuit board device with a dial, a rotor device with a rotor shaftattached to it, a stator device for driving the rotor with the rotorshaft, and an attachment device for attaching the rotor device and thestator device to the printed circuit board in such a way that theprinted circuit board device forms a part of a frame surrounding therotor shaft of the shaft drive deice.

When the shaft drive device is designed in accordance with the presentinvention it

The shaft drive according to the invention has the advantage that it iscompact, especially with a low structural height, and can be producedwith a smaller number of components. It is easy to put together andsimple to contact, for instance by the SMD (surface mounting device)technique. All SMD parts can be assembled automatically, whichsimplifies manufacture substantially.

The concept on which the present invention is based is that the statordevice and the rotor device can be attached to the PCB device in such away that the PCB device forms part of the frame, surrounding the rotorshaft, of the shaft drive device. In particular, this makes it possibleto integrate the axial guidance or bearing of the rotor shaft with thePCB device. Thus the concept according to the invention offers theopportunity of undoing the shaft drive device as an independentcomponent group and partly integrating it into the PCB device instead.

In a preferred refinement, the PCB device has a leadthrough for therotor shaft. It is thus possible to attach the pointer to the rotorshaft on one side of the PCB device and to provide the rotor and thestator device on the other side.

In a further preferred refinement, in the PCB device an axial bearingbush for cooperation with at least one radial bearing bush provided onthe rotor shaft is provided.

In a further preferred refinement, the axial bearing bush is embodied inone piece with the PCB device.

In a further preferred refinement, the axial bearing bush is embodied inan insert that can be received in the PCB device. The stator device canbe attached to this insert in advance in a suitable orientation.

In a further preferred refinement, the rotor shaft can be passed throughthe PCB device from side of the PCB device to a stop, with the rotorremaining on the other side of the PCB device. This simplifies theinstallation of the rotor shaft, since the stop prevents the rotor shaftfrom slipping through.

In a further preferred refinement, the stator device can be attached tothe PCB device all the way around the leadthrough for the rotor.

In a further preferred refinement, the stator device can be attached tothe insert. The insert may be a small precision-manufactured part, towhich the stator device can be attached in a precisely calibrated way.

In a further preferred refinement, the attachment device is designedsuch that it axially supports the rotor shaft on the other side of thePCB device. The force occurring when the pointer is slipped on is thuscounteracted.

In a further preferred refinement, the attachment device has a lid,which can be attached to the other side of the PCB device and which hasan axial bearing bush for receiving the corresponding end of the rotorshaft. Thus two functions can be united in a single component, namely abearing function and a protective function.

In a further preferred refinement, the lid can be locked in the PCBdevice. This is a simple, sturdy way of doing the attaching.

In a further preferred refinement, the stator device can be aligned withthe PCB device via an alignment device, preferably centering pins.

In a further preferred refinement, a spacer can be attached between therotor and the stator device. This spacer assures a correct alignment ofthe rotor and stator device.

In a further preferred refinement, the stator device can be attached bySMD soldering or adhesive bonding to the wiring of the PCB device.

In a further preferred refinement, the stator device forms a unit, whichhas a stator coil core region, a stator winding located thereon, and astator arm region.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention are shown in the drawings anddescribed in further detail in the description below.

Shown are:

FIG. 1, a cross-sectional view of a first embodiment of the shaft drivedevice of the invention, in various stages of assembly;

FIG. 2, a cross-sectional view of a second embodiment of the shaft drivedevice of the invention, in various stages of assembly;

FIG. 3, a view from below of a first example of the stator device,attached to the PCB device and with the rotor device inserted;

FIG. 4, a view from below of a second example of the stator device,attached to the PCB device and with the rotor device inserted;

FIG. 5, a view from below of a third example of the stator device,attached to the PCB device and with the rotor device inserted;

FIG. 6, a view from below of a fourth example of the stator device,attached to the PCB device and with the rotor device inserted; and

FIG. 7, a view from below of a fifth example of the stator device,attached to the PCB device and with the rotor device inserted.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the drawings, the same reference numerals pertain to identical orfunctionally identical components.

FIG. 1 is a cross-sectional view of a first embodiment of the shaftdrive device of the invention, in various stages of assembly.

FIG. 1 shows a printed circuit board or PCB 1; a luminous disk 2; a dial3; a stator device 40 with a stator coil core region 4, a stator winding41, and a stator arm region 42; a rotor device 50 with a rotor 5, arotor shaft 51, and a double radial bearing bush 52; a pointer 8; wiring10 of the PCB device 1; a radial bearing bush 11; a leadthrough 12 forthe rotor shaft 51; a mounting 13 for the dial 3; a stop 15; one hole 16for receiving each detent protrusion; an attachment device 60 with a lid6, an axial bearing bush, and a detent protrusion 62 for the holes 16.

The first embodiment shown in FIG. 1 shows the layout according to theinvention of a stepping motor for an electronic combination instrumentas a pointer drive mechanism; contacting is provided via the wiring 10of the PCB device 1. By the partial integration, according to theinvention, of the shaft drive device with the PCB device 1, the heightof the stepping motor is reduced on the one hand, and its assembly issimplified on the other.

The steps required for assembling the shaft drive device in the firstembodiment will now be described in further detail.

On the PCB device 1, the luminous disk 2 and the dial 3 are attached tothe front side (the top in FIG. 1). The stator device 40 is also mountedon the back side of the PCB device 1, specifically by an SMD joiningmethod, such as adhesive bonding or soldering.

Care must be taken to provide the correct alignment, that is, thecorrect spacing between the rotor 5 and the bunching face of the statorarm region 42 for the magnetic field at the rotor 5. To set this spacingcorrectly, various options exist. In the present example, in reflowsoldering or conductive adhesive bonding of the stator device 40 to thePCB device 1, a mounting rotor (not shown) is carried along, inmagnetized form, and thus assures the correct spacing during themounting process. After the mounting process, the mounting rotor isremoved again.

Once the stator device 40 has been mounted, the insertion of the rotordevice 50 is done, from the back side of the PCB device 1, until theupper radial bearing bush 52 strikes the stop 15 on the upper edge ofthe radial bearing bush 11. Next, the attachment device 60, which in thepresent example comprises the lid 6 with the axial bearing bush 61 andthe detent protrusions 62, is locked in detent fashion or snapped ontothe PCB device 1, in its holes 16.

Once the lid 6 has been mounted on the PCB device 1, the assembly of thestepping motor is concluded, and the assembled component grouprepresents the stepping motor in its known form.

To make the pointer instrument complete, the point 8 is mounted on therotor shaft 51 from the front side of the PCB device 1. On its otherside, the rotor shaft 51 is braced in the axial bearing bush 61 of thelid 6.

FIG. 2 is a cross-sectional view of a second embodiment of the shaftdrive device of the invention, in various stages of assembly.

In FIG. 2, in addition to the reference numerals already given, 1′designates a PCB device embodied differently, that is, with a recess 14,and 101 designates an insert for reception in the recess 14.

In the second embodiment shown in FIG. 2, the axial bearing bush 11′ isembodied in an insert 101 that can be received in the recess 14 of thePCB device 1′. The stator device 40, which forms a unit that has thestator coil core region 4, the stator winding 41 located therein, andthe stator arm region 42, is attached in advance to the insert 101.Since the insert 101 is small, it can be made from a special, extremelydimensionally precise plastic, which in the final analysis assures thecorrect disposition on the PCB device 1′ and thus the correct spacingbetween the rotor 5 and the stator unit 40.

The connection between the insert 101 and the PCB device 1′ isexpediently accomplished both positively and nonpositively by clampingor adhesive bonding or the like.

The remaining layout corresponds to that of the first embodiment in FIG.1.

FIG. 3 is a view from below of a first example of the stator device,attached to the PCB device and with the rotor device inserted.

In FIG. 3, in addition to the reference numerals already given, 45indicates an alignment device in the form of centering pins, and 420indicates a mounting for holding the stator device 40 together.

In the first example of the stator device 40 shown in FIG. 3, the statorarm region 42 extends substantially perpendicular to the stator coilcore region 4. The two halves of the stator device 40 are joined via themounting 420, so that the entire stator device 40 forms a unit, which isattached, aligned by the centering pins 45, to the back side of the PCBdevice 1.

FIG. 4 is a view from below of a second example of the stator device,attached to the PCB device and with the rotor device inserted.

In FIG. 4, in addition to the reference numerals already listed, 110indicates a collar of the PCB device 1 (see FIG. 1) or of the insert 101(see FIG. 2), which acts as a spacer between the rotor 5 and the statordevice 40.

In the second example of the stator device 40 shown in FIG. 4, thespacer 110 is attached between the rotor 5 and the stator device 40, orin other words in the region of the bunching face; the spacer isexpediently a thin plastic ring, on which the stator device 40 restswith its bunching face, virtually without tolerances on the principle ofa spring. The thickness of the spacer 110 is accordingly selected suchthat the rotor 5 can rotate without major frictional resistance.

Otherwise, this second is identical to the first example of the statordevice 40 described in conjunction with FIG. 3.

FIG. 5 is a view from below of a third example of the stator device,attached to the PCB device and with the rotor device inserted.

In FIG. 5, in addition to the reference numerals already listed, 42′designates a modified stator arm region; 43′ designates a setting forthe modified stator arm region 43′; and 420′ designates acorrespondingly modified mounting.

In the third example of the stator device 40 shown in FIG. 5, the twohalves of the stator device 40 are U-shaped, but each of the statorwindings 41 is located in one leg of the U, or in other words the lowerleg in terms of FIG. 5. Also, there is only one mounting 420′ forholding together the two halves of the stator device 40. Settings 43′for receiving the stator arm region 42′ are additional provided on theback side of the PCB device 1.

FIG. 6 is a view from below of a fourth example of the stator device,attached to the PCB device and with the rotor device inserted.

In FIG. 6, in addition to the reference numerals already listed, 42″designates a modified stator arm region and 43″ designates a setting forthe modified stator arm region 43″.

In the fourth example of the stator device 40 shown in FIG. 6, the twohalves of the stator device 40 are V-shaped, with the stator winding 41provided on each leg of the V. In this example, the two halves of thestator device 40 are not joined together; instead, they are fitted intothe corresponding fit 43″ of the PCB device 1, and the centering pins45, as in the above cases, assure the correct alignment.

FIG. 7 is a view from below of a fifth example of the stator device,attached to the PCB device and with the rotor device inserted.

In the fifth example of the stator device 40 shown in FIG. 7, fourstator coil core regions 4 with a corresponding stator winding 41 areprovided, which are at an angle of 90° from one another and do notcohere with one another but instead are attached individually to theback side of the PCB device 1.

Although the above invention has been described above in terms ofpreferred exemplary embodiments, it is not limited to them but insteadcan be modified in manifold ways.

In particular, the shape of the stator device 40 can be variedsubstantially arbitrarily. It is furthermore possible to make theconnection between the stator device 40 and the PCB device 1 in someother way than by the SMD technique. Finally, the pointer 8 can also beattached to the other side of the rotor shaft 51 instead, and in thatcase the stop 15 acts as an axial bearing. The radial bearing bush canalso be attached to the top or the bottom side of the PCB device 1.

What is claimed is:
 1. A shaft drive device for a pointer of a gaugeinstrument, comprising a printed circuit board; a dial arranged on afront side of said printed circuit board in contact with said printedcircuit board; a rotor device with a rotor and a rotor shaft attached tosaid rotor; a pointer arranged on said rotor shaft; a stator device fordriving said rotor with said rotor shaft; an attachment device forattaching said rotor device and said stator device to said printedcircuit board device in such a way that said printed circuit boarddevice forms a part of a frame surrounding said rotor shaft.
 2. A shaftdrive device as defined in claim 1, wherein said printed circuit boarddevice has a leadthrough opening, wherein said rotor shaft passesthrough said leadthrough opening to said dial.
 3. A shaft drive deviceas defined in claim 2, wherein said rotor device is attachable to saidprinted circuit board device about an entire periphery of saidleadthrough opening for said rotor shaft in said printed circuit boarddevice.
 4. A shaft drive device as defined in claim 1, wherein saidrotor shaft extends through said printed circuit board device from aside of said printed circuit board device to a stop, with said rotorremaining on another side of said printed circuit board device.
 5. Ashaft drive device as defined in claim 1, wherein said stator device isattached to an insert.
 6. A shaft drive device as defined claim 5,wherein said attachment device has a lid formed so that it axiallysupports said rotor shaft on an opposite side of said printed circuitboard device.
 7. A shaft drive device as defined in claim 1 and furthercomprising an aligning device which aligns said stator device with saidprinted circuit board device.
 8. A shaft drive device as defined inclaim 7, wherein said aligning device includes centering pins.
 9. Ashaft drive device as defined in claim 1 and further comprising a spacerattached between said rotor and said stator device.
 10. A shaft drivedevice as defined in claim 1, wherein said stator device is attached toa wiring of said printed circuit board device; and further comprisingattaching means for attaching said stator device to said wiring of saidprinted circuit board device and selected from the group consisting ofsoldering attaching means and adhesive attaching means.
 11. A shaftdrive device as defined in claim 1, wherein said stator device is formedas a unit including a stator core coil region, a stator winding locationon said stator core coil region, and a stator arm region.
 12. A shaftdrive device for a pointer of a gauge instrument, comprising a printedcircuit board with a dial; a rotor device with a rotor and a rotor shaftattached to said rotor; a pointer arranged on said rotor shaft; a statordevice for driving said rotor with said rotor shaft; an attachmentdevice for attaching said rotor device and said stator device to saidprinted circuit board device in such a way that said printed circuitboard device forms a part of a frame surrounding said rotor shaft, saidrotor shaft being provided with at least one radial bearing bush, saidprinted circuit board device having an axial bearing bush cooperatingwith said at least one radial bearing bush.
 13. A shaft drive device asdefined in claim 12, wherein said axial bearing bush is formed of onepiece with said printed circuit board device.
 14. A shaft drive asdefined in claim 12, wherein said axial bearing bush is formed as aninsert receivable in said printed circuit board device.
 15. A shaftdrive device for a pointer of a gauge instrument, comprising a printedcircuit board with a dial; a rotor device with a rotor and a rotor shaftattached to said rotor; a pointer arranged on said rotor shaft; a statordevice for driving said rotor with said rotor shaft; an attachmentdevice for attaching said rotor device and said stator device to saidprinted circuit board device in such a way that said printed circuitboard device forms a part of a frame surrounding said rotor shaft,wherein said stator device is attached to an insert, wherein saidattachment device is formed so that it axially supports said rotor shafton an opposite side of said printed circuit board device, and whereinsaid attachment device having a lid which is attachable to a side ofsaid printed circuit board device facing away from said tile and whichhas an axial bearing bush for receiving a corresponding end of saidrotor shaft.
 16. A shaft drive device for a pointer of a gaugeinstrument, comprising a printed circuit board with a dial; a rotordevice with a rotor and a rotor shaft attached to said rotor; a pointerarranged on said rotor shaft; a stator device for driving said rotorwith said rotor shaft; an attachment device for attaching said rotordevice and said stator device to said printed circuit board device insuch a way that said printed circuit board device forms a part of aframe surrounding said rotor shaft, wherein said printed circuit boardhas first and second sides, wherein said dial and said pointer arearranged on said first side of said printed circuit board device andwherein said stator device, said rotor device and said lid are arrangedon said second side of said printed circuit board.